Adhesive bonding and miscellaneous chemical manufacture – Delaminating processes adapted for specified product – Delaminating in preparation for post processing recycling step
Patent
1992-03-17
1994-03-01
Chaudhuri, Olik
Adhesive bonding and miscellaneous chemical manufacture
Delaminating processes adapted for specified product
Delaminating in preparation for post processing recycling step
156DIG115, 222132, 222135, 422249, 422253, C30B 1512
Patent
active
052903958
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a method of and an apparatus for preparing a single crystal of a group III and V compound semiconductor such as GaAs, InP or the like, a group II and VI compound semiconductor such as CdTe, ZnSe or the like, an oxide containing a volatile constituent, or the like.
BACKGROUND OF THE INVENTION
A compound semiconductor single crystal is generally prepared by a horizontal Bridgeman method (HB method) or a liquid encapsulated Czochralski method (LEC method).
When a single crystal is prepared according to the LEC method, such a single crystal is pulled by a rotary pulling shaft from a raw material molten solution having a surface covered with a liquid sealant. An apparatus for such pulling comprises an airtight housing, a rotatable, vertically movable upper shaft having a lower end on which a seed crystal is mounted, a crucible for containing a raw material, a lower shaft for supporting the crucible, an evacuator, an inert gas introducing system, a heater, and the like. In such apparatus, the upper and lower shafts are rotated for providing uniform temperature conditions in the direction of rotation. In addition, the raw material molten solution is covered with a liquid sealant and supplied with a high pressure inert gas, in order to suppress decomposition and evaporation of a raw material element having a high vapor pressure near its melting point.
When a single crystal of a compound semiconductor or the like is prepared by a pulling method, generally employed is a method of filling up a crucible with a raw material polycrystal or a raw material single element or impurity only once at the start and supplying no raw material in an intermediate stage. In such a method, the size of the pulled single crystal is inevitably restricted by the amount of the raw material which is filled into the crucible at the start. In an apparatus for carrying out such a method, the raw material molten solution contained in the crucible is reduced as the pulling proceeds. When the quantity of the molten solution is less than a prescribed value, it is no longer possible to pull a single crystal. If a long single crystal can be grown through single pulling, it is possible to reduce loss at each end of the crystal, while it is also possible to reduce time loss in a preparation step for the crystal growth, an extraction step after the growth and the like. Thus, the cost can be remarkably reduced as compared with a case of growing short crystals repeatedly.
In order to pull a longer single crystal through a single growth step, the crucible must be continuously supplied with the raw material. As to a method of pulling a silicon single crystal, methods enabling a continuous supply of raw materials have been proposed in British Patent No. 755,422 (Aug. 22, 1956), Japanese Patent Laying-Open No. 59-79000 (May 8, 1984), U.S. Pat. No. 4,659,421 (Apr. 21, 1987), U.S. Pat. No. 2,977,258 (Mar. 28, 1961) and U.S. Pat. No. 4,650,540 (Mar. 17, 1987), for example.
Each of these methods utilizes a wide crucible to pull a single crystal from a certain pulling region of the crucible while dissolving a solid raw material in another region of the crucible for supplying the same into the pulling region. When the supply quantity of the solid raw material is substantially equal to the pulling quantity, the crucible is regularly provided therein with a constant quantity of the raw material molten solution. Thus, it is possible to pull a silicon single crystal until the solid raw material is used up or the pulling reaches the geometrical limit of the upper shaft in the apparatus. Since it is possible to grow a sufficiently long ingot of a silicon single crystal, the cost for preparing the single crystal can be reduced.
Each of these apparatuses is adapted to pull a single crystal from and supply a solid raw material into the same crucible. The crucible is formed to have a wide surface area and a thin bottom. While the crucible is rotatable about its central axis, the center of the pulling shaft is not
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Kawase Tomohiro
Matsumoto Kazuhisa
Tatsumi Masami
Chaudhuri Olik
Fasse W. G.
Garrett Felisa
Sumitomo Electric Industries Ltd.
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